Ch 7 Section 1 Flashcards
common names usually give no information about
chemical composition
to describe atomic makeup of compounds chemists use
systematic methods for naming compounds and for writing chemical formulas
for a molecular compound, the chemical formula reveals the number of atoms of each element contained in a
single molecule of the compound
an ionic compound consists of a lattice of
positive and negative ions held together by mutual attraction
the chemical formula for an ionic compound represents one formula unit–the
simplest ratio of the compound’s positive ions and its negative ions
parentheses surround the polyatomic anion to
identify it as a unit
when there is no subscript written next to an atom’s symbol, the value of the subscript is
understood to be 1
monatomic ions are ions formed from a
single atom
not all main-group elements readily
form ions
atoms of carbon and silicon form
covalent bonds in which they share electrons with other atoms
other elements tend to form ions that do not have
noble-gas configurations.
elements from the d-block form
2+, 3+, 1+, or 4+ cations
Many d-block elements form two
ions of different charges
monatomic cations are identified simply by
the elements name
in naming monatomic anions the ending of the element’s name is
dropped and replaced with -ide
numerals used in the naming of ions are part of the
stock system of naming chemical ions and elements
binary compounds are compounds composed of
two elements
in a binary ionic compound the total numbers of positive charges and
negative charges must be equal
the formula for a binary compound can be written given the
identities of the compound’s ions
in binary ionic compounds the charges of the compounds are not
included in the formula
crossing over is a method of balancing the
charges between ions in an ionic compound
Step 1 for cross over method
write the symbols for ions side by side, with cation first
step 2 for cross over: cross over the
charges by using the absolute value of each ion’s charge as the subscript for the other ion
step 3 for cross over: check the subscripts and divide them by their
largest common factor to give the smallest possible whole-number ratio of ions. then write the formula
nomenclature
naming system
the nomenclature of binary ionic compounds involves combining the names of the
compound’s positive and negative ions
for most simple ionic compounds, the ratio of the ions is not indicated in the compound’s name because it is
understood based on the relative charges of the compound’s ions
some elements form two or more
cations with different charges
to distinguish ions formed by elements that form 2 or more cations with different charges, scientists use the
stock system of nomenclature
stock system uses a roman
numeral to indicate an ions charge
numeral is enclosed in parentheses and is
placed immediately after the metal name
names of metals that commonly form only one cation do not
include a Roman numeral
there is no element that commonly forms more than
one monatomic anion
oxyanions are polyatomic ions that
contain oxygen
the name given a compound containing an oxyanion depends on the
number of oxygen atoms in the oxyanion
(oxyanions) the name of the ion with the greater number of oxygen atoms ends in
-ate
(oxyanions) the name of ion with smaller number of oxygen atoms ends in
-ite
sometimes an element can form more than two types of
oxyanions
an anion that has one fewer oxygen atom than the -ite atom has is given the prefix
hypo-
an anion that has one more oxygen atom that the -ate anion has is given the prefix
per-
compounds containing polyatomic ions are named in the same manner as
binary ionic compounds
unlike ionic compounds molecular compounds are composed of individual
covalently bonded units (molecules)
chemists use two nomenclature systems to name
binary molecules
he newer system is the stock system for naming molecular compounds, which requires
an understanding of oxidation numbers
the old system of naming molecular compounds is based on the use of
prefixes
mono-
1
di
2
tri
3
tetra
4
penta
5
hexa
6
hepta
7
octa
8
nona
9
deca
10
(rules for prefix system) element that has the smaller group number is usually
given first
(rules for prefix system) if both elements are in the same group, the element whose period number is greater is
given first
(rules for prefix system) the element is given a prefix only if it
contributes more than one atom to a molecule of the compoudn
(rules for prefix system) the second element is named by combing (a) a prefix indicating the
number of atoms contributed the element, the root of element’s name, and ending-ide
(rules for prefix system) with few exceptions, the ending ide indicates that a compound contains only
2 elements
(rules for prefix system) the o or a at the end of a prefix is usually dropped when the word following begins with
another vowel
in covalent network compounds there are no distinct
units
the subscripts in a formula for covalent-network compound indicate the
smallest whole-number ratio of the atoms in the compound
an acid is a distinct type of
molecular compound
most acids used in the lab can be classified as either
binary acids or oxyacids
binary acids are acids that consist of
two elements, usually hydrogen and one of the halogens
oxyacids are acids that contain
hydrogen, oxygen, and a third element (usually nonmetal)
the term acid typically refers to a solution in water of one of these
special compounds rather than to the compound itself
many polyatomic ions are produced by the loss of hydrogen
ions from oxyacids
a salt is an ionic compound composed of a
cation and the anion from an acid
some salts contain anions in which
one or more hydrogen atoms from the acid are retained
such anions are named by adding the word
hydrogen or prefix bi- to anion name
